Acquisitions and Divestitures - Pro Forma (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended	4 Months Ended	9 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2013 Nonvoting Common Stock [Member]	Apr. 30, 2012 Nonvoting Common Stock [Member]	Apr. 30, 2013 Nonvoting Common Stock [Member]	Apr. 30, 2012 Nonvoting Common Stock [Member]	Apr. 30, 2013 Precision Dynamics Corporation [Member]	Apr. 30, 2013 Precision Dynamics Corporation [Member]	Apr. 30, 2013 Precision Dynamics Corporation [Member]	Apr. 30, 2012 Precision Dynamics Corporation [Member]
Business Acquisition [Line Items]
Total inventories	$ 16,788		$ 16,788						$ 1,530	$ 1,530	$ 1,530	$ 1,530
Interest Expense	4,185	4,735	12,755	14,715							529	720
Income Tax Expense (Benefit)											(135)	(827)
Business Combination, Acquisition Related Costs											3,600	3,600
Net sales	305,737	275,388	856,408	813,573					40,682	56,750
Net sales, pro forma	305,737	319,077	924,832	938,774
Income (Loss) from Continuing Operations Attributable to Parent	21,838	28,039	37,669	84,328	21,778	27,982	37,490	84,156
Earnings from continuing operations, pro forma	21,838	29,893	42,553	83,271
Income (Loss) from Continuing Operations, Per Basic Share					$ 0.42	$ 0.53	$ 0.73	$ 1.60
Basic net (loss) income per Class A Common Share, pro forma (USD per share)	$ 0.42	$ 0.57	$ 0.83	$ 1.58
Income (Loss) from Continuing Operations, Per Diluted Share					$ 0.42	$ 0.53	$ 0.73	$ 1.59
Diluted net (loss) income per Class A Common Share, pro forma (USD per share)	$ 0.42	$ 0.56	$ 0.82	$ 1.57
Amortization of Intangible Assets	$ 6,597	$ 3,944	$ 15,759	$ 12,102							$ 9,313